LTC1726 LINER [Linear Technology], LTC1726 Datasheet - Page 5

• Manufacturer Part Number: LTC1726
• Description: Triple Supply Monitor and uP Supervisor with Adjustable Reset and Watchdog Timer
• Manufacturer: LINER [Linear Technology]

PI FU CTIO S
V
power to the part when the voltage on this pin is greater
than the voltage on V
with a 0.1 F or larger ceramic capacitor.
V
supplies power to the part when the voltage on this pin is
greater than the voltage on V
ground with a 0.1 F or larger ceramic capacitor.
V
also supplies power to the part when the voltage on this
pin is greater than the voltage on V
ground with a 0.1 F or larger ceramic capacitor.
V
it can be tied to either V
GND (Pin 4): Ground.
WDI (Pin 5): Watchdog Input. A logic input whose rising
or falling edge must occur on this pin within the selected
watchdog time-out period or a reset pulse will occur. The
watchdog time-out period is set by the value of the
capacitor that is placed on the WT pin. The rising or falling
edge of this pin clears the voltage on the WT capacitor,
preventing a reset pulse from occurring. If the watchdog
TYPICAL PERFOR A CE CHARACTERISTICS
CC3
CC5
CC25
CCA
U
(Pin 3): 1V Sense, High Impedance Input. If unused
(Pin 2): 5V Sense Input (LTC1726-5). This pin also
(Pin 1): 3.3V Sense Input. This pin also supplies
(Pin 2): 2.5V Sense Input (LTC1726-2.5). This pin
U
10
10
10
10
10
10
6
5
4
3
2
0.1
U
Time-Out Period vs Capacitance
CC25
T
A
= 25 C
CC3
/V
1
CC5
, V
W
C
CC5
. Bypass this pin to ground
RT
10
CC3
OR C
U
or V
CC3
. Bypass this pin to
WT
10
. Bypass this pin to
(pF)
CC25
t
2
WT
.
10
t
RT
3
1726 G12
10
4
timer is not cleared, a reset pulse will occur. The watch-
dog timer is cleared during a reset and restarts when the
reset is deasserted. When disabling the watchdog func-
tion, this pin should be connected to either V
ground and WT must be grounded.
RST (Pin 6): Reset Logic Output. Active low, open-drain
logic output with weak pull-up to V
one or more of the supplies are below trip thresholds.
After all supplies become valid, the reset remains as-
serted for the period set by the capacitor on the RT pin.
The watchdog timer can also trigger the reset whenever
the watchdog time-out period is exceeded. This pin can
be pulled up greater than V
logic.
WT (Pin 7): Watchdog Time-Out Input. Place a capacitor
between this pin and ground to adjust the watchdog time-
out period. To determine the watchdog time-out period:
with t
capacitor will generate a 1s watchdog time-out period.
The watchdog function can be disabled by connecting
this pin to ground.
t
WT
WT
= 21.8 • C
3
2
1
0
0
RST Output Voltage vs
Supply Voltage (LTC1726-2.5)
in s and C
V
10k PULL-UP FROM V
T
A
CC3
= 25 C
= V
CC25
WT
1
= V
CCA
V
WT
CC3
CC3
(V)
2
in pF. As an example, a 47nF
TO RST
CC3
when interfacing to 5V
3
1726 F13
CC3
. Asserted when
LTC1726
CC3
5
or